Synovial fluid: sampling
Synonym(s): Arthrocentesis, Joint fluid collection
Introduction
- An essential adjunct to the investigation of joint disease; aims to differentiate degenerative, infectious and immune-mediated conditions.
Uses
- Articular effusions, polyarthritis, joint stiffness, joint pain.
- Investigation of pyrexia of unknown origin.
Normal synovial fluid is of small volume (<1 ml in dogs), clear, viscous, pale or pale straw colored and does not clot on standing.
Advantages
- Immediate subjective assessment of color and viscosity.
- Differentiates major classifications of joint disease, ie infectious from non-infectious and inflammatory (neutrophilic) from degenerative disorders.
- Multiple joints may be sampled.
- Does not usually require general anesthesia.
Disadvantages
- Yields small volumes of fluid, therefore may need to sample more than one joint.
- All joints require analgesia.
- Multiple sampling of a single joint may confuse interpretation due to iatrogenic bleeding.
Technical problems
- Requires some experience for sampling of some joints, eg coxofemoral.
Alternative techniques
- Synovial membrane biopsy Biopsy: synovia, can provide more definitive diagnosis in some cases of inflammatory arthropathy and synovial tumors.
- Arthroscopy, in large joints for visualization of joint surfaces and collection of biopsy material.
- Arthrotomy can give a more complete assessment of traumatic injuries to the hard and soft joint tissues.
Time required
Preparation
- 5 min site preparation.
Procedure
- Minimum 5 min depending on joint to be sampled and experience of technician in locating and entering joint space.
Decision taking
Criteria for choosing test
- Radiographs that indicate pathology in specific joint.
- Obviously enlarged joint.
Risk assessment
Do not enter joint with overlying skin infection or lesion.
- Additional diagnostic information for difficult to diagnose lameness or fevers.
Requirements
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Preparation
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Technique
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Aftercare
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Montgomery R D, Long I R Jr., Milton J L et al (1989) Comparison of aerobic culture, synoval membrane biopsy and blood culture medium in detection of canine bacterial arthritis. Vet Surg 18 (4), 300-303 PubMed.
- Pedersen N C (1978) Synovial fluid collection and analysis. Vet Clin North Am 8 (3), 495-499 PubMed.